1. Field of the Invention
The present invention relates to manufacturing management, and in particular to a system and method of manufacturing planning and control with a fixed planning schedule for an order using a statistical process control (SPC) method.
2. Description of the Related Art
Supply chain is important for modern enterprises, systemizing purchase of materials, transformation of materials into intermediate and finished products, and distribution of finished products. In the supply chain, customers transmit requests (demands) consisting of a request for a particular quantity of a product by a specific date to a manufacturer, and the manufacturer plans its manufacturing schedule according to these received requests to satisfy each customer.
Supply chain management has become an important issue to meet the goals of reduced inventory and increased productivity. Conventionally, resources and facilities of a production system are regarded as limiting factors. Therefore, not every customer request may be met, since some may be promised, some may suffer inadequate supply, and others rejected. Consequently, effective demand and capacity management in supply chain management without excess capacity loss has become fundamental and critical for most manufacturing and distribution organizations.
Supply chains exist in most manufacturing environments, although the complexity of the chain may vary greatly from industry to industry and firm to firm. For integrated circuit (IC) foundries, the manufacturing process of each IC product is complicated and varies and the cost of wafers and capacity is relatively high.
Many commercial supply chain solution providers provide packaged systems for clients to install and follow, such as i2 technology or ADEXA Inc. For a manufacturer or a factory, a production scheduling engine is usually embedded in the systems to arrange resources and materials for a production plan. The production scheduling engines provide a master production schedule (MPS) for the manufacturer or factory to follow. However, conventional production scheduling engines are designed to meet the best interests of the manufacturer or factory. More specifically, conventional production scheduling engine are programmed to generate a minimum-cost, optimal-capacity, and low-inventory MPS.
For IC foundries, conventional production scheduling engines recalculate and generate an updated MPS to optimize resources and capacity when receiving new orders. When lots are running (hereinafter referred as work-in-process, WIP), the MPS is still changed, indicating rolling production schedules for running lots for optimization of foundry resources. It becomes difficult to promise delivery of their lots because of the rolling MPS.
When a preferable plan engine is provided so that the rolling MPS can be accurately obtained, however, manufacturing execution in the production system may not match the manufacturing plan, due to problems in execution, such as unfamiliarity on the part of the manufacturer with the production system, or problems in planning, such as ill-defined parameter settings provided to the plan engine.
Generally, a checking process between manufacturing plan and execution in the production system is required to match the plan and execution. However, it is difficult to determine whether problems with the production system occur in the planning engine or manufacturing execution when a significant deviation is found. Specifically, problems may occur in execution, but the manufacturing plan may be mistakenly modified to match the execution.
For clients, the uncertainty can severely disrupt transport and inventory planning and management.